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Molecular characterization of hprt mutations from chinese hamster ovary cells treated with 1‐, 3‐, and 6‐Nitrosobenz[ a ]pyrene
Author(s) -
Zhan DeJin,
Chiu LiHsueh,
Heflich Robert H.,
Fu Peter P.
Publication year - 1998
Publication title -
environmental and molecular mutagenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1
H-Index - 87
eISSN - 1098-2280
pISSN - 0893-6692
DOI - 10.1002/(sici)1098-2280(1998)31:1<60::aid-em9>3.0.co;2-f
Subject(s) - chinese hamster ovary cell , microbiology and biotechnology , biology , genetics , mutant , exon , base pair , gene , mutation , chinese hamster , dna , cell culture
1‐, 3‐, and 6‐Nitrobenzo[ a ]pyrene (nitro‐BaP) are environmental contaminants that can be metabolized to genotoxic derivatives by either nitroreduction or ring‐oxidation. In this study, we examined the types of mutations produced by the primary nitroreduced metabolites, 1‐, 3‐, and 6‐nitroso‐BaP (NO‐BaP) in the hprt gene of Chinese hamster ovary cells. RNA from 6‐thioguanine‐resistant mutants was reverse‐transcribed to cDNA and the hprt coding sequence was amplified and sequenced. The mutational patterns produced by the three compounds exhibited extensive similarities: 1) base pair substitutions accounted for 67% (28/42) of 1‐NO‐BaP, 51% (26/51) of 3‐NO‐BaP, and 50% (11/22) of 6‐NO‐BaP mutations; 19–36% of the mutations were exon deletions and 14–18% were frameshifts; 2) most (64–84%) of the simple base pair substitutions occurred at G:C, mainly G:C → T:A and G:C → C:G tranversions; 3) 98% (46/47) of the simple base pair substitutions at G:C had the mutated dG on the non‐transcribed strand and 81% (38/47) were located with the mutated dG flanked 3′ by at least one purine; and 4) most simple base pair substitutions (48/62, 77%) occurred in exons 2, 3, and 8 of the hprt gene. Although there were no significant differences among the mutation profiles of the NO‐BaPs, a significant difference did exist between the mutation pattern produced by 3‐NO‐BaP and the mutation pattern previously determined for the ring‐oxidized product of 3‐nitro‐BaP metabolism, trans ‐7,8‐dihydroxy‐anti‐9, 10‐epoxy‐7,8,9,10‐tetrahydro‐3‐nitrobenzo[ a ]pyrene. This observation indicates that differences in the structures of closely related adducts can be important enough to hae an effect on mutation profiles. Environ. Mol. Mutagen. 31:60–69, 1998. Published 1998 Wiley‐Liss, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.